Cleaning metal surfaces



Patented Mar. 16, 1943 2,314,285 CLEANING mar. summons Oliver M. Morgan,

Allied Chemical 8; tion of New York No Drawing.

Snyder, N. Y., assignor to Dye Corporation, a corpora- ApplicationMal'ch so, 1938,

Serial No. 198,909 -18 Claims. (Cl. 204F145 This invention relates to improvements in the cleaning of metal surfaces. It relates more particularly to improvements in the removal of grease, oil and similar dirt of various kinds coal tar distillate,

taining non-aqueous solvents for greases; asfor example, trichloroethylene, petroleum distillates;

vents have many (herein designated by the inclusive term greasy p m ny of m are inflammable; the residues) from the surfaces of. metal objects as p s f ma y f them a e to o men; 1 a step in the fabrication of the metal into a and h y usually require expensive y m for finished product having a coating on the surface the recovery and purification of the soiled solof the metal. vents for reuse. Further, in connection with the An object of the invention is to provide 1m- 10 cleansing of many steel surfaces, a form'of dirt provements in the cleansing of metal surfaces known s y finely divided carbon) whereby economies in the cleansing process may 18 left adhering to e metal after e cleaning be effected. treatment, especially when the steel has-been Additional obje ts of the invention are to r subjected to a previous acid treatment. .1 vide improvements in alkaline cleansing baths Withaview toovercoming these disadvantage for removing grease, 11 and imfla d t from processes have been devised for cleansing metalmetal surfaces whereby th cleansing aetion of surfaces, and particularly ferrous metal surfaces, said alkaline baths may be increased; to provide wherein the m l je s to be cl aned are improvements in uch alkalin cleansing at immersed in an aqueous alkaline bath which is whereby the rapidity of cleansing metal surfaces 0 heated to e a y'h s t mp rature." in some by aid bath may be increased; t provide 1 cases after subjecting the metal objectsto a m v t i such m m cleansing baths preliminary treatment with an organic solvent. whereby th power 1 said baths t retain s when themetal is removed from the treatment moved oil, grease and dirt without impairment bath it is Washed with w t r t m ve adherin of the effectiveness of said baths as cleansing 111811118 ns l qu r- It is then in a' clean agents for metal may be increased; and to condition ready for further aqueous treatments vide improvements in such alkaline cleansing Y 8 P to further treatmentbaths whereby increased effectiveness of said 3met1me5 the treatment in h aqueous baths as cleansing agents for metal surfaces may line bath is carried out in coniunctien h the be btain d i connection t t use of said passage of an electric current through the bath, baths in cleansing processes involving electrothe metal Objects being a the anode the lytic tio cathode, whereby the electrolytic action, together oth objects f t invention 111 in part be with such additional mechanical action as may ob and 111 in part appear heremgften result from the passage of the electric current M processes for t fabricatio of met-a1 (e. g., formation of bubbles and agitation by the products i v lv an r ti in which a coating gases liberated at the surface .of the metal) aids is applied to the surface of metal, either for proin the removal of undesired i pu ities from the t ti or decorative purposes Thus, metal metal surface. The action of the hot alkali on jects of various sources and fabricated from the 5011 adhering to the metal rface in some ferrous or non-ferrous metals are electroplated, 10 cases effects sflponificetien 0f h Oil or grease, painted enameled lacquered or otherwise treated or in other cases producesan emulsiflcation of to provide a finished article comprising a m t the dirt, according to the chemical nature of the surface having coating of another metal or of constituents of the soil. When the treatment is other coating material applied thereto. In consupplemented y the Passage of an electric curnection with the fabrication of such coated metal rent throush the aqueous i e bath serving articles, it is essential that the surface of the es the electrolyte an electrolytic ll in which metal subjected to. the application of the coating the meta-1 be cleaned 15 made the od 'or be freefrom grease, oil, scale and dirt Of all kinds cathode, the gases generated on the surface" of which would tend to interfere with the uniform the m tal e h adh ring foreign substances, adherence of the coating to the surface of the and inesome cases the metal Surface Itself may t be modified by formation of a film of oxide, or by o method her tofore proposed for eleanmg reduction of oxides which may be on the surface metal surfaces to prepare them for subsequent 01 the metal to the metal i ac ording as the treatment, and particularly coating thereof, inmetal to be cleaned is made the anode or th volves immersing the metal objects in baths concathode of the cell.

etc. Such non-aqueous soldisadvantages however; for

The aqueous alkaline solutions resulting from the cleansing of the metal surfaces is employed for the treatment of additional soiled metal until the concentration of dirt, grease, saponification products. and/or other soil in the bath becomes so great as to interfere with the eflicient action of the bath.

According to the present invention improvements in the cleansing of metal surfaces by the use of aqueous alkaline baths are effected by incorporating into the aqueous alkaline baths higher alkyl aromatic sulfonates of the type hereinafter more fully described. I have found, in accordance with the present invention, that the presence of higher alkyl aromatic sulfonates of said type in alkaline solutions employed for cleaning metal surfaces increases the cleansing power of said solutions, as a result of which the said solutions are enabled to degrease and cleanse the metals more speedily and more effectively. I have further found, in accordance with the present invention, that the presence of higher alkyl aromatic sulfonates of said type in the alkaline solutions employed for cleaning metal surfaces increases the ability of said alkaline solutions to disperse, emulsify and/or absorb soil removed from the metal surfaces, as

a result of which the effective period of usefulness of said alkaline cleaning solutions is greatly increased. I

The amounts of said higher alkyl aromatic sulfonates necessary to effect the improvements are small and are usually only a fraction of the amount (on a weight basis) of the alkaline substances present in alkaline aqueous cleansing solutions.

I have also found, as a further feature of the present invention. that by reason of the emulsifying action of said higher alkyl aromatic sulfonates toward organic substances which are solvents for grease and oil and which are normally insoluble in'water, such organic solvents can be emulsified in alkaline aqueous solutions, and accordingly alkaline aqueous cleansing solutions can be prepared containing both organic solvents and alkali; thereby making it possible to secure the cleansing action of both types of cleansing agents in a single aqueous cleansing bath. The following organic compounds exemplify some of the types of organic solvents which can be used in the metal cleaning proc esses and compositions of this invention:

Tetrahydronaphthalene Hexahydronaphthalene Decahydronaphthalene Butyl acetate Diethylene glycol monoethyl ether Diethylene glycol monomethyl ether Diethylene glycol monobutyl ether Ethylene glycol monoethyl ether Ethylene glycol monomethyl ether Ethylene glycol monobutyl ether Dibutyl phthalate Dichlorethyl ether Ethylene dichloride Isopropyl alcohol N-hexyl alcohol Methyl amyl alcohol Octyl alcohol Methyl amyl acetate Ethylene glycol monomethyl ether acetate Ethylene glycol monoethyl ether acetate Perchlorethylene (tetrachlorethylene) Stoddard solvent The higher alkyl aromatic sulfonates which may be employed in the practice of the present invention are the alkyl derivatives of aromatic monoand polysulfonic acids and their salts, containing at least one nuclear alkyl radical of 7 or more carbons. (The term nuclear as employed herein refers to substituents for hydrogen atoms in the aromatic nucleus.)

The aromatic nuclei of said higher alkyl aromatic sulfonates may be mononuclear (i. e., a member of the benzene series) or polynuclear, whether condensed polynuclear (e. g., of the naphthalene series, etc.) or uncondensed polynuclear (e. g., of the diphenyl series). They may contain 1 or more nuclear alkyl radicals of 7 or more carbon atoms, and 1 or more nuclear sulfonate groups (sulfonic acid groups or salts thereof). They may be free from further substituents or they may contain 1 or more additionalnuclear substituents. Examples of such additional nuclear substituents are halogen, and hydroxyl, lower alkyl, alkoxy, carboxyl (in the free acid or salt form), aryloxy, amino and alkylamino groups.

The higher nuclear alkyl radical is preferably an aliphatic hydrocarbon radical containing at least 10 carbon atoms. hydrocarbon radical containing a straight or branched carbon chain, or it may be a cyclo aliphatic radical.

Examples of such higher alkyl aromatic sulfonates are:

Potassium heptyl naphthol sulfonate Sodium methyl-cyclohexyl naphthalene sulfonate Sodium lauryl naphthalene sulfonate Sodium cetyl benzene sulfonate Ammonium dodecyl phenetol sulfonate in which X represents hydrogen, halogen, or one of the groups hydroxyl-, alkyl-, alkoxy-, (e. g., methoxy-, ethoxy-, benzyloxy-, etc.) aryloxy (e. g., phenoxy, etc.) carboxy-, aminoand alkylamino-; R represents an alkyl hydrocarbon radical, saturated or unsaturated, containing ten or more, and preferably ten to nineteen carbon atoms; and M represents hydrogen, or a metal or an ammonium or organic ammonium radical. For convenience, they are hereinafter referred to as monoalkyl aromatic sulfonates of the benzene series," which term generically includes said sulfonates, whether in the form of the free sulfonic acids or their salts.

Preferred compounds employed in accordance with the present invention are the mixed monoalkyl aromatic sulfonates of the benzene series in which the higher alkyl radicals correspond with the aliphatic hydrocarbons of petroleum distillates, and similar products, boiling above C., and which are obtainable by halogenatiom of a petroleum distillate or similar It may be an open chain 4 suiting solution neutral to Brilliant Yellow and, Congo Red papers) and evaporating the neuproduct, and especially of an aliphatic hydrocarbonmixture of the Pennsylvania petroleum kerosene type of which at least 80 per cent boils above 17.0 0., followed by condensation ofresuiting mixed alkyl halides with an aromatic compounds (e. g., benzene, phenol, cresols, phenetol, etc.), preferably with the aid of a metal halide condensing agent, and suiionation of re- .mine, etc.- If the salt-forming basic component is polybasic, it may be neutralized in part with the above defined suli'onic acids and in part by other suitable acidic materials.

The following example illustrates a method of preparing aikyl. aromatic sulfonates useful in connection with the present invention. It will be evident from a consideration ofv the disclosure herein that the invention is not limited to the I use of products prepared in this manner but includes products of the type referred to herein when prepared in other ways. The parts are by weight and temperatures are in degrees centigrade. 1

Example 1 v A hydrocarbon fraction boilingfrom 180 to 300 and obtained from a Pennsylvania crude oil was chlorinated in the presence of catalytic amounts of iodine at a temperature below 60. The. chlorination was continued until the specific gravity of the chlorinated hydrocarbon reached 0.92. This corresponds to an average of one and one-quarter atoms of chlorine per molecule of hydrocarbon. 2035 parts of this chlorinated hydrocarbon'were rapidly added to a mixture of 1320 parts of benzene and 132' parts of anhydrous aluminum chloride. The mixture was agitated for 5 hours and then allowed to stand overnight. The oil was decanted from the aluminum chloride sludge and washed with an equal volume of water. The unreacted benzene and a part of the unreacted petroleum distillate were removed by distilling up to 100 at 25 mm.

pressure. The remaining oil was mainly a mixture of alkyl derivatives of benzene. 400 parts of the resulting mixed alkyl derivatives of benzene-were sulfonated with 330 parts of-26 per cent oieum by adding the oieum to the oil at andthen agitating at room temperature for two and one-half hours. The mixture was then allowedto stand forrabout a half hour and the upper layer of unsulfonated material was drawn oil. The lower sulfonate layer was then added to 110 parts of ice keeping the temperature below 35 and allowed to stand for about 2 hours, or until residual sulfuric acid separated from ,the alkyl benzene sulfonic acids. The residual sulfuric acid was drawn off and the mixed alkyl benzene sulfonic acids were recovered in the form of sodium salts by neutralizing with sodium hydroxide (for example, by treatment with a 50 per cent aqueous solution of caustic soda in an amount suilicient to render the retralized solution to dryness. In a similar manner, other salts of the .mixed alkyl benzene sulfonic acids can be obtained.

Other examples of methods of preparing alkyl aromatic sulfonates useful in connection with thepresent inventlon are disclosed .inUnited States PatentsNos. 2,195,409, 2,196,985, 2,249,757

and 2,283,199.

The following 'eXamplesiIIustrate the use the products herein described. It will be un-' derstood, however, that these examples are merely illustrative and that any of the, other monoalkyl aromatic sulfonates herein disclosed may be similarly employed.

EzampleZ An alkaline metal-cleaning solution was prepared by dissolving caustic soda and alkaline 1 The ingredients employed consalts in water. sisted of the following, in parts by ,weightz' Caustic soda (NaOH) 10 Trisodium phosphate (Na3PO4.12H2O) -30 Sodium meta silicate '(NaaSiOa.5HzO) 20 Soda ash' (Na-200a) 40 The proportions of ingredients employed were in the ratio of 6 ounces of theresulting mixture per U. S. gallonof water. To the resulting solution,

one-third ounce was added of the product of Example 33 of United States Patent No. 2,196,985

(comprising about 45 per cent of sodium higher alkyl phenol sulfonates and about 55. per cent of inert salts, mainly sodium sulfate), equivalent to about one-sixth ounce on a salt-free basis). and the resulting solution was heated to between F. and the boiling point of the solution.

Greasy iron plate wasimmersed in the re'sult ing hot alkaline solution for 2 to '6, minutes, thenv removed and rinsed in water. The resulting iron plate was free from grease and dirt and was 1 ready for further processing. When subjected to,

electroplating with nickel, uniformlyadherent nickel coatings were obtained.

The alkaline solution was repeatedly used for the cleansing of greasy iron plates for a total period of three and one-half weeks before it had to be discarded because of accumulated impurities. Under the same conditions of treat-j ment a'solution to which the said alkyl phenol sulfonate'product was notadded, but which was otherwise the same, had to be discarded after a.

total period of only two weeks.

' Example 3 A similar alkaline metal-cleaning solution was prepared by employing one-third ounce of the product of Example 9 of United States Patent 'No. 2,249,757 in preparing the alkaline metalcleaning solution of Example 2. The resulting solution had similar advantageously rapid and effective cleansing action on greasy iron plate,

4 and emulsifying and dispersing action on the removed soil.

Example 5 A similar alkaline metal-cleaning solution was prepared by employing one-third ounce of the product of Example 2 oi! United States Patent No. 2,195,409 in preparing the alkaline metalcleaning solution of Example 2. The resulting solution had similar advantageously rapid and effective cleansing action on greasy iron plate, and emulsifying and dispersing action on the removed soil.

Example 6 Alkaline metal-cleaning solutions were prepared by employing the same components as outlined in Examples 2, 3, 4 and 5 in the same amount, and mixing with these solutions 1 to ounces of any one of the organic solvents listed at bottom of p. 2, col. 1, for each U. 8. galbe emulsified with the alkaline cleaning solution employed- It will be realized by those skilled in the art that changes may be made in the processes and compositions hereinbefore described without departing from the scope of the invention.

Thus the ingredients and proportions thereof employed in the preparation of the alkaline compositions may be varied. For example, any of the following mixtures of alkalies may be employed instead of those employed in above Examples 2, 3, 4, 5 and 8: 1

Triso- Sodium Caustic Soda Alkaline mixture No. soda .r dllj-El I SEE :26 h

1 1o 55 as 1 l0 50 40 8.... n 10 50 30 10 The proportions of the above alkaline constituents and those employed in Examples 2, 3, 4, 5, and 6 may vary from 3 ounces to 10 ounces of the alkaline mixture per U. 8; gallon of water.

The higher alkyl aromatic sulfonates employed in accordance with the present invention have the advantage of being stable even in hot alkaline solutions and of forming salts with a number of heavy metals, which salts are soluble in the alkaline cleaning baths. They may therefore be used in a wide variety of alkaline metal cleaning processes under a variety of conditions. The amount of higher alkyl aromatic sulfonate employed in Examples 2, 8, 4, 5 and 8 may vary from 56 to 1 ounce of higher alkyl aromatic sulfonate (on a salt-free basis) per U. 8. gallon of The compositions of Examples 2, 3, 4, 5 and 6 and their equivalents can be used as electrolytic baths for the cleansing ofmetals by an electrolytic process in which the metal to be cleansed is made the anode-or cathode. When employed for 2,s14,ses

maintained between 10 amperes and 40 amperes per square foot of surface being cleaned and the temperature of the bath is preferably adjusted to between 160 F. and 212 F. The presence of the higher alkyl aromatic sulfonates in such electrolytic baths increases the rapidity and effectiveness of the cleaning.

I claim:

1. In the process of cleaning metal surfaces involving removal of greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises carrying out the metal cleaning with the aid of an alkaline aqueous solution containing a small amount of an alkyl aromatic sulfonate having at least 7 carbon atoms in an alkyl radical, as a cleansing assistant and as an emulsifying agent for the residues.

2. In the process of cleaning metal surfaces involving removalof greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises subjecting the metal to be cleaned to the cleansing action of ahot aqueous alkaline solution containing a small amount of an alkyl aromatic sulfonate having 10 to 19 carbon atoms in an alkyl radical, as av cleansing assistant and as an emulsifying agent for the residues.

3. In the process of cleaning metal surfaces involving removal of greasy residues by treatment this purpose, the current density is preferably 15 with analkaline aqueous cleansing composition, the improvement which comprises immersing the metal to be cleaned in a hot aqueous alkaline cleansing bath containing a monoalkyl aromatic sulfonate of the benzene series having at least 7 carbon atoms in an alkyl radical in an amount not exceeding one ounce of said sulfonate per gallonof water, as a cleansing assistant and as an emulsifying agent for the residues.

4. In the process of cleaning metal surfaces involving removal of greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises immersing the metal to be cleaned in a hot aqueous alkaline cleansing bath containing caustic alkali and alkaline salts in asmall amount and a lesser amount of a monoalkyl aromatic sulfonate of the benzene series having 10 to 19 carbon atoms in an all-- involving removal of greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises immersing the metal to be cleaned in a hot aqueous alkaline cleansing bath containing caustic alkali and alkaline salts in' a small amount and a lesser-amount of a mixture of monoalkyl aromatic sulfonates of the benzene series in which the alkyl radicals have at least 10 carbon atoms and correspond with the aliphatic hydrocarbons of petroleum distillates, as a cleansing assistant and as an emulsifying agent for the residues, the amount of the mixture of sulfonates not exceeding one ounce per gallon of water.

6. In the process of cleaning metal surfaces involving removal of greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises immersing the metal to be cleaned in a hot aqueous alkaline cleansing bath containing caustic alkali and alkaline salts in a small amount and a lesser amount of a mixture of monoalkyl aromatic sulfonates of the benzene series in which the alkyl radicals have 10 to 19 carbon atoms and correspond with the aliphatic hydrocarbons sition, mersing the metal amount exceeding one'ounce per gallon of water.

' '7. In the process of cleaning metal surfaces involving removal of greasy residues by treatment with an alkaline aqueous cleansing compothe improvement which comprises imto be cleaned in a hot aqueous alkaline cleansing bath containing per galion of water one-eighth to one ounce of an alkyl aromatic sulfonate having at least 7 carbon atoms in an alkyl radical, as a cleansing assistant and as an emulsifying agent for the residues, while passing an electric current through said bath and through said metal as an electrode.

8. In the process of cleaning metal surfaces involving removal of greasy residues by treatment with an alkaline aqueous cleansing composition. the improvement which comprises immersing the metal to be cleaned in a hot aqueous alkaline cleansing bath containing caustic alkali and alkaline salts in a small amount and a lesser amount of a monoalkyl aromatic sulfonate of the benzene series having 10 to 19 carbon atoms in an aliphatic hydrocarbon radical, as a cleansing assistant and as an emulsifying agent for the residues, the amount of the sulfonate not exceeding one ounce per gallon of water,

while passing an electric current through said bath and through said metal as an electrode.

9. In the process of cleaning metal surfaces involving removal or greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises carrying out the metal cleaning with the aid of an alkaline aqueous solution containing a small amount oi! an alkyl aromatic sulfonate having at least '7 carbon atoms in an alkyl radical, as a cleansing assistant and as an emulsifying agent for the residues, and containing an organic liquid which is a solvent for grease and oil and which is insoluble in water, emulsified in said solution by means of said alkyl aromatic sulfonatei 10. In the process of cleaning metal surfaces involving removal of greasy residues by treatment with an alkaline aqueous cleansing composition, the improvement which comprises subjecting the metal to be cleaned to the cleansing action oi! a hot aqueous alkaline solution con- ,tain'ing a mixture of monoalkyl aromatic sulionates of the benzene series in which the alkyl radicals have 10 to 19 carbon atoms and correspond with the aliphatic hydrocarbons 01 petroleum distillates, as a cleansing assistant and sulfonate having at least 7 carbon atoms in an alkyl radical, the amount of the suifonate not exceeding one ounce per gallon of water.

12. A metal-cleaning composition comprising an aqueous alkaline solution containing caustic alkali and alkaline salts and an alkyl aromatic sulfonate having 10 to 19 carbon atoms in an alkyl radical. the amount of the sulfonate not as an emulsifying agent. for the residues, the

of the mixture of sulfonates not exceeding one ounce per allon of water, and containing a small amount or an organic liquid which is a solvent for grease and oil and which is insoluble in water, emulsified in said solution by means of said mixture of sulfonates.

11; A metal-cleaning composition comprising an aqueous alkaline solutioncontaining caustic alkali and alkaline salts and an alkyl aromatic exceeding one ounce per gallon of water.

13. A metal-cleaning composition comprising an aqueous alkaline solution containing caustic alkali and alkaline salts in a small amount and a lesser amount 'of a monoalkyl aromatic sulfonate of the' benzene Series having at least 10 carbon atoms in an alkyl radical, the amount of the sulfonate not exceeding one ounce per gallon of water.

14. A metal-cleaning composition comprising an aqueous alkaline solution containing caustic alkali and alkaline salts in a small amount and a lesser amount or a monoalkyl aromatic sulfonate oi the benzene series having 10 to 19 carbon atoms in an aliphatic hydrocarbon radical, the amount or the sulfonate not exceeding one ounce per gallon of water.

15. A metal-cleaning composition comprising an aqueous alkaline solution containing caustic alkali and alkaline salts in a small amount and a lesser amount or a mixture of monoalkyl aromatic sulfonates of the benzene series in which the alkyl radicals have at least 10 carbon atoms and correspond with the aliphatic hydrocarbons of petroleum distillates, the amount of the mixture of sulfonates not exceeding one ounce per gallon of water.

16. A metal-cleaning composition comprising an aqueous alkaline alkali and alkaline salts in a small amount and a lesser amount or a mixture of monoalkyl aromatic sulfonates of the benzene series in which the alkyl radicals have 10 to 19 carbon atoms and correspond with the aliphatic hydrocarbons of petroleum distillates, the amount or the mixture of sulfonates not exceeding one ounce per gallon 01 waten 17. A metal-cleaning composition comprising an aqueous alkaline solution containing in admixture therewith a small amount of an organic liquid which is a solvent for grease and oil and which is insoluble in water, and an alkyl aromatic sulfonate having at least 7 carbon atoms in an alkyl radical in an amount not exceeding one ounce of said sulfonate per gallon of water.

18. A metal cleaning composition comprisin an aqueous alkaline solution containing caustic alkali and alkaline salts and a' small amount or an organic liquid which is a. solvent for grease and oil and which is insoluble in water, emulsified in said solution by means of a mixture of monoalkyl aromatic sulfonates of the benzene series in which the alkyl radicals have 10 to 19 carbon atoms and correspond with the aliphatic hydrocarbons of petroleum distillates, the amount of the mixture of sulfonates not exceeding one ounce per gallon of water.

OLIVER M. MORGAN.

solution containing caustic 

